Do We Really Need Another Satellite Orbiting the Moon?

NASA has successfully guided 12 astronauts to the surface of the moon, where they explored their surroundings and set up numerous surveys and studies. Earth-based telescopes have had no trouble recording physical details of the lunar surface. Recently, Japan sent Kayuga, a high-tech satellite that has returned the most detailed maps of the moon to date. Now NASA plans on sending another satellitethe Lunar Reconnaissance Orbiter. Do we really need more data on our already well-documented celestial neighbor? Here, a comparison of LRO and Kayuga addresses the question.

It is a tale of two satellites, a shared destination, and two very different missions. Here on Earth, one lunar orbiter prepares to begin its voyage to the moon. Meanwhile, 235,000 miles away in space, the other plummets from orbit endings its mission in a heap on the lunar surface.

This week at Cape Canaveral, Florida, NASA will launch its Lunar Reconnaissance Orbiter (LRO). Presently strapped to the top of an Atlas V rocket at the Kennedy Space Center, it is the $579 million opening salvo of the space agency's "Vision for Space Exploration," the series of missions initially intended to return Americans to the moon, then eventually take them further into space. John Keller, a deputy scientist with the LRO mission, says the objective of the project is to determine whether it's safe--and if essential resources like water exist--to proceed with the plan to colonize the moon.

The Kaguya orbiter, launched by the Japanese space agency (JAXA) in late 2007, had strictly scientific objectives. The agency set out to answer some of the moon's remaining unsolved mysteries, not to mention be the first to map the moon using the latest in digital imaging technology. "LRO is not a science mission," Jim Garvin, chief scientist at the Goddard Space Center and one of LRO's founding fathers, told Popular Mechanics. "It has high science value, but it was conceived to provide engineering parameters for our eventual manned return to the moon."

Though the orbiters share a few similar instruments--both, for example, boast high-resolution cameras and laser altimeters to provide unprecedented, richly detailed topographic models of the lunar surface--the unique objectives of the mission mean that even seemingly comparable devices actually differ significantly.

"The scientific community is awaiting the tremendous data sets that will come from each of these missions," Keller says. But while the Kayuga data will be extremely useful to NASA, Garvin adds, "What we need to know is the terrain at civil engineering scales; temperatures, which they're not mapping; hydrogen, as a resource, at a few miles scale; imaging at the scale of a rock that will break a lander leg. When you start putting all those things together, it's beyond what you want in a general science mission."

>KAYUGALROCOST
$279 million
$579 millionOBJECTIVE
To obtain scientific data on lunar origins and evolution, and to develop the technology for future lunar exploration.
To find safe landing sites, locate potential resources, characterize the radiation environment, and demonstrate new technology.LIFESPAN
21 months (September 2007 to June 2009)
1 to 4 years (1 year exploration goal, with possibility of extended mission lasting 3 years)CAPABILITIES

Lunar Radiation: A Charged Particle Spectrometer on Kaguya collected data on high energy particles as they peppered the moon, so that scientists might forecast radiation from cosmic rays.

>Magnetic Anomalies: Perched at the end of a 12-meter mast, the Lunar Magnetometer obtained measurements on the varied direction, strength and intensity of the moon's magnetic fields, providing the data to produce the most detailed maps of the moon's magnetic anomalies.

>Gravity Fields: Measurements of the interference in signals sent between Kaguya, a pair of sub-satellites (Usuda and Okina), and radio dishes on Earth provided data on the moon's gravity, and created the first complete maps covering the entire moon's gravitational make-up.

>Lunar History: The Lunar Radar Sounder, a device emitting low frequency (5MHz) radio pulses into the moon, was used to analyze stratification below the surface, thus providing data for better understanding the moon's tectonic past.

>HDTV: Kaguya employed a high definition television camera to film the first ever HD video of the lunar surface, and also capture a full Earth-rise as it orbited the moon.

>Topography: A suite of imaging equipment, the Terrain Camera (TC) and Multi Band Imager (MI), swept over the surface in a continuous "push-broom" fashion. The TC was comprised of two, one-dimensional telescopes and captured black-and-white images with an unprecedented resolution of 10m/pixel. At the same time, a Laser Altimeter attached to the orbiter sent a constant laser pulse to the surface. By timing the reflection between the surface and the orbiter, the altimeter collected precise data used to create the first-ever "global, accurate and precise topographic map of the Moon."

Measuring Radiation: Two devices will measure the moon's volatile radiation environment. Similar to Kaguya's Charged Particle Spectrometer, the Lunar Explorer Neutron Detector (LEND), will measure the neutron flux produced by the barrage of cosmic rays that constantly showers the lunar surface. But LRO goes a step further with the Cosmic Ray Telescope for the Effects of Radiation (CRaTER). It will not only detect incoming solar particles as they pass the orbiter, but also carry a layer of Tissue Equivalent Plastic, specially engineered to simulate human tissue and measure the biological effects of particle bombardment.

>Search for Ice: The LRO has several instruments aimed at determining whether or not water, in the form of ice, exists on the moon. Diviner, a radiometer, will create the first global temperature survey of the lunar surface, detecting cold traps where ice may exist. According to Garvin, it will "tell us where the super cold places are, and how cold they really are. No other mission is doing that, but it's really a fundamental question."

A new technology display called Mini RF, a small antenna attached to LRO, will send radio waves to the moon's poles, the signals that return will then be analyzed to determine whether ice is trapped in the poles' deep, unmapped craters. The Lyman-alpha Mapping Project (LAMP) will measure the faint reflection of light created by stars and hydrogen atoms in space to determine the composition of the moon's permanently unlit regions.

>Search for Landing Sites: While Kaguya's cameras and altimeter created topographic models of exceptional, never-before-seen clarity and detail, NASA aims to better them. Its Lunar Orbit Laser Altimeter (LOLA) will provide terrain mapping data for choosing future landing sites. "It's not like the ones that have flown before," Garvin says. "It will actually map things at a spatial scale of just a few meters, and 10cm vertically. That's the scale [with which] we map ice sheets on the Earth."

The LRO's camera package consists of one wide angle lens with 100m/pixel resolution, along with a pair of narrow angle scopes with 50cm/pixel resolution. Together they will capture extremely detailed views--objects as small as 1 meter will be visible. "The cameras on the now impacted Japanese mission make mapping at a scale of like 15 meters, 20 meters, not 50 centimeters," Garvin says. "We will be able to make integrated maps of landing site regions that will predict safety and allow for better design of future landing systems. We massively over-designed Apollo because we had to. Now, we can be smarter."